Micro Electro-Mechanical Systems (MEMS) for use in optical switching applications typically contain optical mirrors that are controllable electronically. The optical mirrors are typically micro-machined from a silicon wafer and coated with various materials to produce a reflective mirror surface. The mirror structure is typically bonded onto a substrate, and the resulting structure is typically packaged within a glass-covered package. The glass allows light to pass to and from the optical mirrors.
The substrate typically includes electrode pads that are used to control the position of the optical mirrors, and also includes various electrical contacts. When the mirror structure is bonded onto the substrate, the electrical contacts on the substrate need to make contact with electrical contacts on the mirror structure, and the optical mirrors must be positioned a precise distance above the electrode pads. This is because the voltage required to position a mirror depends on the distance of the mirror from the electrode pads, and variations in the distance between the mirrors and the electrode pads make it difficult to control the position of the mirrors.